Hydraulic control arrangement

ABSTRACT

A hydraulic control arrangement provided with a control valve having a spool movable between a neutral position which closes at least one conduit leading to a consumer device and two working positions, in one of which it connects the conduit with a fluid inlet passage and in the other of which it connects the conduit with a fluid return passage. The hydraulic control arrangement includes a switch valve communicating with the fluid inlet and the fluid outlet of the arrangement and having a valve member biased by a spring to a position in which flow of fluid from the inlet to the outlet through the switch valve is prevented. The position of the valve member is further controlled by a pair of throttles arranged in a control conduit communicating with the switch valve and arranged and constructed in such a manner that undesirable pressure increases during fine regulation of fluid flow passing through the control valve to the consumer device are prevented.

United States Patent [1 1 1111 3,924,655

Schwerin Dec. 9, 1975 HYDRAULIC CONTROL ARRANGEMENT [57] ABSTRACT Inventor: Giillthel' Schwerin, Mbglingen, A hydraulic control arrangement provided with a con- Germany trol valve having a spool movable between a neutral [73] Assignee Robert Bosch GmbH German position which closes atleast one conduit leading to a y consumer device and two working positions, in one of Flled: Jan. 17, 1974 which it connects the conduit with a fluid inlet passage 21 A I. N 434 343 and n the other of Wl'llCh 1t connects the condult w1th 1 pp 0 a fiu1d return passage, The hydraulic control arrangement includes a switch valve communicating with the [30] Foreign Application Priority Data fluid inlet and the fluid outlet of the arrangement and Jan. 24, 1973 Germany 2303286 having a valve member biased y a Spring to a PQSitiOH in which flow of fluid from the inlet to the outlet 52 US. (:1 137/596.13; 137/625.69 through the Switch valve is prevented The posit-ion of [51 Int. cm F15B 13/04 the valve member is further controlled y a p of [58 Field of Search 60/468, 494; 91/451; throttles arranged in a Control Conduit communicating 137/62569 59612 596 13 with the switch valve and arranged and constructed in such a manner that undesirable pressure increases [56] Refe Cit d during fine regulation of fluid flow passing through the UNITED STATES PATENTS control valve to the consumer device are prevented.

3,722,543 3/1973 Tennis l37/596.l2

Primary ExaminerAlan Cohan Assistant ExaminerGerald A. Michalsky Attorney, Agent, or FirmMichael S. Striker '7 Claims, 5 Drawing Figures /lV sweetly,

HYDRAULIC CONTROL ARRANGEMENT BACKGROUND OF THE INVENTION The present invention relates to a hydraulic control arrangement with a control valve for controlling flow of fluid to a consumer device. The control valve has a control member which in a neutral position closes at least one conduit leading to a consumer device, whereas in two working positions of the control member the conduit is selectively connectedwith a fluid inlet or a fluid return passage. The arrangement includes further a switch valve arranged to permit the pressure fluid fed into the inlet of the arrangement to pass directly into the fluid outlet and a control passage coordinated with the switch valve. Flow of fluid through the control passage is controlled by the control member of the control valve and a throttle is arranged in the control passage which produces a pressure difference resulting in a force acting on the valve member of the switch valve against the force of a spring biasing the valve member of the switch valve to a position preventing direct flow from the inlet to the outlet through the switch valve.

A control arrangement of the aforementioned kind is known in the art in which the positionof thevvalve member of the switch .valve is hydraulically controlled. In this arrangement, the control member of the control valve is in form of a spool movable in axial direction and provided with a pluralityiof sections or piston portions formed with cutouts of gradually varying cross section for fine adjustment of the flow of fluid passing to the consumer device and the flow of fluid passing through the control passage of the arrangement. However, this known arrangement doesnot permit a satisfactory fine control of the aforementioned fluid streams. The reason for. this non-satisfactory performance of the known control arrangement is that, depending on the position to which the spool ismoved, there will result, independent from the fluid pressure in the consumer device at any time, pressure increases in the fluid until the sum of the fluid stream passing to the consumer device and the fluid stream passing through the control passage will'be equal to the flow of fluid fed into the inlet of the arrangement. Such undesired pres-- sure increases in control arrangements with switch valves detrimentally influence the fine adjustment of the fluid flow obtainable from the arrangement or load the pump feeding fluid into the arrangement in an un-- desirable manner.

SUMMARY OF THE INVENTION With these and other objects in view, which will become apparent as the description proceeds, thehydrau lic control arrangement ac cording to the present inven:

tion mainly comprises switch valve means communicating with the fluid inlet and the fluidoutletof. thearrangement and having a valve member movablebetween an open position permitting flow of fluidfrom 2 the inlet to the outlet through the switch valve means and a closed position preventing such flow, and spring means biasing the valve member to the closed position, first control passage means communicating with the A inlet and the switch valve and connected in parallel to the latter so that fluid passing through the first control passage acts on the valve member in the same direction as the spring means, second control passage means communicating at one end with the first control passage means, a first throttle in said first control passage means upstream of said one end of said second control passage means, a second throttle in said first control passage means upstream of the first throttle, return flow passage means communicating at one end with the outlet and adapted to communicate at the other end with the other end of the second control passage means, inlet passage means communicating at one end with the first control passage means between the first and the second throttle therein, and control valve means having a control member movable between a neutral position in which it closes at least one conduit leading to a consumer device and working positions to opposite sides of said neutral position for selectively connecting the aforementioned conduit with the inlet passage means or the return flow passage means, said control member also regulating flow from said second control passage means to said return flow passage means and from said inlet passage means to the aforementioned conduit of the consumer device.

In this way it is possible, as will be explained later on in detail, to avoid undesirable pressure increases during fine regulating the fluid flow through the arrangement while at the same time this fine regulating of the fluid flow is considerably improved. In addition, the advantages of having a switch valve by means of which the directly switched over to the outlet may be fully used.

An additional advantage of the hydraulic control arrangement according to the present invention is that it can be manufactured at reasonable cost and that it can be incorporated into known hydraulic controlarrange merits of the prior art without too great difficulties.

It; is especially advantageous when the second throt tle is provided with a greater open cross section than the first throttle. The mentioned advantages will especially occur if it is possible to influence, with a very small fluid flow flowing through the control passages, a very-large fluid flow in the region in which such fluid flow is regulated in fine manner.

The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a schematic partially sectioned view of the hydraulic control arrangement according to the present invention;

FIG. 2 is a diagram illustrating the pressure variations independence on the position of the control member of the control valve for different pressures in the consumerdevice in a control arrangement according to the prior art',

FIG. 3 is a diagram illustrating theamount of fluid flowing through the arrangement in dependence on the position of the control member for different pressures in the donsumer device in an arrangement according to the prior art;

FIG. 4 is a diagram similar to FIG. 2 for the control arrangement according to the present invention; and

FIG. 5 is a diagram similar to FIG. 3 for a control arrangement according to the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The hydraulic control arrangement illustrated in FIG. 1 comprises a connecting plate 11, a control valve 12 and an end plate 13, arranged in abutting relationship as shown in FIG. 1, and connected to each other in any convenient manner, not shown in the drawing.

A switch valve 14 is arranged in the connecting plate 11 which communicates at one end with a fluid inlet 15 and intermediate its ends with a fluid outlet 16. A valve member 17 of the switch valve 14 is biased by means of a spring 19 in the pressure chamber 18 of the valve in closing direction in which a control edge 21 of the valve member is moved to a position preventing flow from the inlet 15 to the outlet 16 through the switch valve. A first control passage 22 communicates at opposite ends with the inlet 15 and the pressure chamber 18. A first throttle 23 is provided in this control passage and a second throttle 25 is arranged in the first control passage 22 upstream of the first throttle. The second throttle 25 has a greater open cross section than the first throttle 23. A first branch passage 220 branches off from the first control passage 22 downstream of the first throttle 23 and a second branch passage 22b branches off from the first control passage 22 between the first and the second throttle, which branch conduits end at the face 24 at which the connecting plate 11 abuts against the control valve 12. The connecting plate 11 is further formed with a passage 27 leading from the outlet 16 to the aforementioned face 24. A

pressure limiting valve 26 arranged in the connecting.

plate communicates at opposite ends with the aforementioned passage 27 and the inlet 15.

The control valve 12 has a housing 28 with a longitudinal bore 29 formed therethrough, which is at longitudinally spaced portions thereof enlarged to form an inlet chamber 31, two consumer chambers 32 and 33, two return flow chambers 34 and 35 and two adjacent control chambers 36 and 37. The inlet chamber 31 is connected by a passage 39, in which a check valve 38 is arranged, with the branch passage 22b. The two return flow chambers 34 and 35 are connected to each other by a passage 41. The chamber 34 is further connected by a passage 42 to the return flow passage 27 in the connecting plate 11. A passage 43 connects the control chamber 36 with the branch passage 22a in the connecting plate 11. A passage 44 leads from the control chamber 37 to the face of the housing 28 which abuts against the end plate 13. A passage 56 formed in the end plate 13 connects the aforementioned passage 44 with a passage 42a leading from this end face into the return flow chamber 34. A pair of conduits 58 and 59 respectively lead from the chambers 32 and 33 through the housing 28 and the end plate 13 to aconsumer device, not shown in the drawing. A valve spool 45 is closely guided in the cylinder bore 29 and the spool is provided with a plurality of spaced piston sections, the outer surfaces of which engage the inner surface of. the bore, The control edges 48 of the piston sections 46 and 47 are provided with cutouts or chamfers 49 which taper in the direction away from the respective control edge for controlling flow of fluid from the chambers 31 and 33 to the conduits 58 and 59. Two additional piston sections 51 and 52 are provided with similar cutouts or chamfers 54 at their control edges 53 for controlling flow of fluid from the passage 43 into the passage 44. A double acting return device 55 biases the spool 45 to the neutral position, as shown in FIG. 1, from which it is movable in opposite directions to a plurality of working positions.

The branch passage 22a together with the passages 43, 44, the control chambers 36 and 37 and the passage 56 form part of the second control passage means 57 leading from the inlet 15 to the outlet 16. The passages 22b and 39 form part of inlet passage means connecting the first control passage with a conduit leading to a consumer device.

The above described control arrangement will operate as follows:

In the neutral position of the spool 45, as shown in the drawing part of the pressure medium fed into the inlet 15 may flow through the second throttle 25, the first throttle 23 and the open second control passage 57 into the outlet 16. The pressure difference created mainly at the first throttle 23 presses the valve member 17 against the force of the spring to the open position so that most of the fluid medium passes, only partly throttled, from the inlet 15 directly into the outlet 16. The fluid medium stream which passes through the control passage means 57 is held substantially constant by the first throttle 23 in cooperation with the switch valve 14.

If the valve spool 45 of the control valve 12 is moved toward the right, as viewed in FIG. 1, the control edge 53 on the piston section 51 with its cutout or chamfer 54 will throttle flow of fluid through the control passage means 57. This will cause the pressure in the pressure chamber 18 to rise and therewith also the pressure at the inlet 15. When now the pressure at the inlet 15 surpasses the sum of the pressure of the consumer device and the resistance of the check valve 38, pressure fluid will flow from the inlet 15, through the second throttle 25, the passages 22a and 39, the inlet chamber 31, past the control edge 48 of the piston section 47, into the consumer chamber 33. At the same time, the pressure medium flowing back from the consumer device may pass from the other consumer chamber 32 into the return flow chamber 34 and from there through the passages 42 and 27 to the outlet 16. Due to the pressure medium stream which flows to the consumer device, an additional pressure difference will be created-at the second throttle 25. The total pressure drop produced by the first and the second throttle 23 and 25 will be determined by the spring 19 and will remain constant for each position of the valve member 17. In other words, the pressure of the fluid medium at the inlet 15 will act at one end of the valve member 17, tending to move the valve member toward the right, as viewed in FIG. 1, whereas the force of the spring 19 and the fluid pressure reduced by the pressure drop at the first and the second throttle will act on the other end of the valve member 17, tending to move the latter toward the left. Since the pressure drop in the second throttle 25 will increase when fluid passes from the inlet through the passages 22b and 39 into the chamber 31, thecombined force acting on the right end of the valve member 17 will be reduced corresponding to the increased pressure drop produced by the second throttle 25. This will result that the control edge 21 of the valve member 17 will throttle flow from the inlet to the outlet 16 through the switch valve to a decreasing degree, which in turn will result in a reduced pressure increase at the inlet so that such pressure increases can be prevented in a much more effective manner than it was possible up to now.

The diagram of FIG. 4 illustrates the mentioned increase of the pressure p at the inlet 15 in dependency on the displacement s of the spool 45 according to curve 61 and depending on different pressures of the consumer device according to the curves 6265. The pressure increase at the transition from the line 62 to the lines 62-65 is thereby, due to the influence of the second throttle 25 relatively small, this influence will increase with increased displacement of the spool 45.

FIG. 2 illustrates the corresponding curves 66-69 for a control device according to the prior art which does not have a second throttle 25. The pressure increase proceeds along the curve 61 at low pressure in the consumer device up to a multiple of the pressure in the consumer device before it drops down again according to the curves 66-69 to the predetermined consumer device pressures. At a high pressure in the consumer device, the pressure increase will lead to an opening of the pressure limiting valve as can be noticed from the flattening of the curve 69.

The FIGS. 3 and 5 illustrate the change of the amount of fluid flow q in dependence on the deflection s of the spool 45 in a control arrangement according to the prior art, respectively in the control arrangement of the present invention at different pressures in the consumer device.

The curves of FIG. 5 are considerably flatter than those of FIG. 3, since the influence of the pressure increase is substantially eliminated by the second throttle. The fine control produced by the spool 45 operates therefore in a manner which is greatly improved as compared with a control arrangement according to the prior art.

The spool 45 will evidently also cooperate with the other elements of the disclosed control arrangement to produce a very fine control of the fluid passing therethrough when the spool 45 is moved from its neutral position towards the left.

It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of hydraulic control arrangements differing from the types described above.

While the invention has been illustrated and described as embodies in a hydraulic control arrangement, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.

Thus, for instance, the valve member 17 may to gether with the pressure limiting valve 26 form a precontrolled pressure limiting valve. The control valve 12 may also be constructed in different manner as above described and be provided with a control member cooperating with a plurality of valve seats. In both constructions of the control valve it is immaterial whether the desired control function will be performed by a single control member or by two control members which are spaced from each other.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can, by applying current knowledge, readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.

What is claimed as new and desired to be protected by Letters Patent is set forth in the appended:

l. A hydraulic control arrangement comprising a fluid inlet and a fluid outlet; switch valve means communicating with said inlet and said outlet and having a valve member movable between an open position permitting flow of fluid from said inlet to said outlet through said switch valve means and a closed position preventing such flow, and spring means biasing said valve member to said closed position; first control passage means providing constant communication between said inlet and said switch valve means and connected in parallel to the latter so that fluid passing through said first control passage means acts on said valve member in the same direction as said spring means; second control passage means communicating at one end with said first control passage means; a first throttle in said first control passage means upstream of said one end of said second control passage means; a second throttle arranged in said first control passage means upstream of said first throttle and having an open crosssection which remains constant during operation; return flow passage means communicating at one end with said outlet and adapted to communicate at the other end with the other end of said second control passage means; inlet passage means communicating at one end with said first control passage means between said first and said second throttle therein; and control valve means having a control member movable between a neutral position in which it closes at least one conduit leading to a consumer device and working positions at opposite sides of said neutral position for selectively connecting said conduit with said inlet passage means and said return flow passage means, said control member regulating also flow from said second control passage means to said return flow passage means and from said inlet passage means to said conduit.

2. A hydraulic control arrangement as defined in claim 9, wherein said control member in said neutral position permits free flow of fluid from said second control passage means to said return flow passage means and in each of said working positions throttles such flow.

3. A hydraulic control arrangement as defined in claim 1. wherein said control member of said control valve means is in the form of an elongated spool movable in axial direction between said positions thereof, said spool having sections provided with cutouts of gradually varying cross section for fine regulating flow of fluid passing through said second control passage means.

4. A hydraulic control arrangement as defined in claim 3, wherein said spool has further sections provided with cutouts of gradually varying cross section for fine regulating flow of fluid from said inlet passage means to said conduit.

5. A hydraulic control arrangement as defined in claim 4, wherein the open cross section of said second throttle means is at least such that, when said second flow passes from said inlet passage means to said conduit, the force resulting from the pressure drop at said second throttle and acting on said valve member of said switch valve is only slightly smaller than the force of said spring means.

7. A hydraulic control arrangement as defined in claim 1, wherein said second throttle has an open crosssection which is greater than that of the first throttle. 

1. A hydraulic control arrangement comprising a fluid inlet and a fluid outlet; switch valve means communicating with said inlet and said outlet and having a valve member movable between an open position permitting flow of fluid from said inlet to said outlet through said switch valve means and a closed position preventing such flow, and spring means biasing said valve member to said closed position; first control passage means providing constant communication between said inlet and said switch valve means and connected in parallel to the latter so that fluid passing through said first control passage means acts on said valve member in the same direction as said spring means; second control passage means communicating at one end with said first control passage means; a first throtTle in said first control passage means upstream of said one end of said second control passage means; a second throttle arranged in said first control passage means upstream of said first throttle and having an open crosssection which remains constant during operation; return flow passage means communicating at one end with said outlet and adapted to communicate at the other end with the other end of said second control passage means; inlet passage means communicating at one end with said first control passage means between said first and said second throttle therein; and control valve means having a control member movable between a neutral position in which it closes at least one conduit leading to a consumer device and working positions at opposite sides of said neutral position for selectively connecting said conduit with said inlet passage means and said return flow passage means, said control member regulating also flow from said second control passage means to said return flow passage means and from said inlet passage means to said conduit.
 2. A hydraulic control arrangement as defined in claim 9, wherein said control member in said neutral position permits free flow of fluid from said second control passage means to said return flow passage means and in each of said working positions throttles such flow.
 3. A hydraulic control arrangement as defined in claim 1, wherein said control member of said control valve means is in the form of an elongated spool movable in axial direction between said positions thereof, said spool having sections provided with cutouts of gradually varying cross section for fine regulating flow of fluid passing through said second control passage means.
 4. A hydraulic control arrangement as defined in claim 3, wherein said spool has further sections provided with cutouts of gradually varying cross section for fine regulating flow of fluid from said inlet passage means to said conduit.
 5. A hydraulic control arrangement as defined in claim 4, wherein the open cross section of said second throttle means is at least such that, when said second control passage means is closed by said spool while a maximum fluid flow passes from said inlet passage means to said conduit, the force resulting from the pressure drop at the second throttle and acting on said valve member of said switch valve is smaller than the force of said spring means.
 6. A hydraulic control arrangement as defined in claim 4, wherein the open cross section of said second throttle is such that, when said second control passage means is closed by said spool while a maximum fluid flow passes from said inlet passage means to said conduit, the force resulting from the pressure drop at said second throttle and acting on said valve member of said switch valve is only slightly smaller than the force of said spring means.
 7. A hydraulic control arrangement as defined in claim 1, wherein said second throttle has an open cross-section which is greater than that of the first throttle. 